Ok well I'm pretty new to all this and Im trying to find some help for my engine knocking..I know that toyota recommends not exceeding psi of 8 pounds running through the turbo at constant rates on the stock engine..And I know they are right because I often run around 11 -15 psi and usually get engine knocking after constant pressures at this level...So basically Ill Im trying to figure out is if this is a common problem with the 1989 Toyota Supra Mk3 turbo? Can anyone suggest what may be my problem? What can I do to help this problem? Thanks! -Thomas